The present invention relates to a clutch control device of a hybrid vehicle.
A hybrid vehicle equipped with an engine and a motor has various driving modes including an EV driving mode, a series driving mode, and a parallel driving mode. As shown in FIGS. 8 to 10, such hybrid vehicle includes a clutch 35 that engages/releases an engine shaft 32 at an engine 31 side with/from a motor shaft 34 at a motor 33 side, and the hybrid vehicle maintains the clutch 35 in an engaged state/a released state based on the driving mode (see, for example, Japanese Patent No. 3702897B). Any one of a wet type (single plate/multi-plates) and a dry type (single plate/multi-plates) may be used as the clutch. Hereinafter, both types will be referred to as the clutch.
Herein, referring to FIGS. 8 to 10, the relationships between each of the driving modes and the clutch will be described.
In the EV driving mode, a tire 36 of a vehicle 30 is driven by driving the motor 33, as shown in FIG. 8. In this case, the engine 31 stops, electric generation by a generator 37 also stops, and the clutch 35 is in the released state.
In the series driving mode, electricity is generated by the generator 37 by driving the engine 31, and the motor 33 is driven by using electricity generated by the generator 37 as well as electricity charged in a battery (not shown) so that the tire 36 of the vehicle 30 is driven, as shown in FIG. 9. Even in this case, the clutch 35 is in the released state.
Meanwhile, in the parallel driving mode, the tire 36 of the vehicle 30 is driven by driving the engine 31, and the clutch 35 is in the engaged state. As a result, the driving force of the engine 31 is transmitted to the motor shaft 34 side (drive shaft side), as shown in FIG. 10. In the parallel driving mode, the tire 36 of the vehicle 30 may be driven by driving both the engine 31 and the motor 33.
As described above, the vehicle 30 is driven while the clutch 35 is released and the engine shaft 32 and the motor shaft 34 are in a mechanical power-off state, in the EV driving mode and the series driving mode in which the motor 33 is used as a driving force. In contrast, in the parallel driving mode in which the engine 31 is used as a driving force, the vehicle 30 is driven while the clutch 35 is engaged and the engine shaft 32 and the motor shaft 34 are mechanically coupled to each other.
Accordingly, when the driving mode is switched from the EV driving mode or the series driving mode to the parallel driving mode, the clutch 35 having been released is engaged, whereas when the driving mode is switched from the parallel driving mode to the EV driving mode or the series driving mode, the clutch 35 having been engaged is released.
A maximum driving force of an engine 31 has a predetermined value depending on a vehicle velocity, whereas a maximum driving force which can be outputted by a motor 33 depends on not only the vehicle velocity but also a possible battery output which can be outputted by a battery (a detailed description will be made in FIGS. 2 to 4 to be described below). When the driving mode switches from the parallel driving mode to the series driving mode, a driving force shifts from the engine 31 to the motor 33 by releasing the clutch 35 having been engaged. However, just after the clutch 35 is released, if the possible battery output is not considered, there is a large difference between the maximum driving force of the engine 31 and the maximum driving force which can be outputted by the motor 33, and a torque shock occurs, such that the hybrid vehicle is not comfortable to drive.